Question

Antedon belongs to the class
A. Crinoidea
B. Asteroidea
C. Ophiuroidea
D. Echinoidea

Answer 1

Hint: Antedon are free-swimming crinoids that are stemless. The genus appeared first in the Cretaceous period in the fossil record. The morphological characteristics of Antedonids found in various environments have great variability.

Complete answer: There are no stems in members of the genus Antedon, but five pairs of feathery arms emerge from the central concave disk. On the upper surface, the mouth and the ambulacral grooves are present. Clawed cirri have a temporary attachment to the substrate on the lower surface. The name ‘Crinoidea’ derives from the word ‘a lily’ in ancient Greek, with the suffix-oid meaning ‘like’. Both live in shallow water. Crinoids are marine animals that makeup one of the Echinodermata phylum classes; the Crinoidea class, starfish, brittle stars, sea urchins and sea cucumbers are also included. Those crinoids that are connected by a stalk to the sea bottom in their adult form are generally referred to as sea lilies, while the unstalked types are called feather stars or comatulids, being part of the larger sea bottom. Feather stars are part of Crinoidea. Antedon is a star with a feather.
So, option A is the correct answer.

Note: There are only about 600 living species of crinoids, but in the past, the class has been much more abundant and varied. Some thick limestone beds are made up almost entirely of disarticulated fragments of crinoids from the mid to the late Paleozoic period.